This invention relates to high performance complementary metal oxide semiconductors (CMOS) and/or very short channel length, ultra shallow source/drain metal oxide semiconductor (MOS) transistors and, more particularly, to an integrated circuit device including an epitaxial nickel silicide on (100) Si or a stable nickel silicide on amorphous Si wherein cobalt is utilized as an interlayer in the fabrication of the silicide, and to a method of manufacturing the same.
Titanium silicide and cobalt silicide are each currently being used in salicide manufacturing processes to produce metal oxide semiconductor (MOS) transistors. Titanium silicide has a disadvantage in that it is difficult to transform the silicide to a low resistivity C54 phase when the polysilicon line width is reduced. Cobalt silicide has the disadvantage of a high silicon (Si) consumption rate to form cobalt disicilide. Therefore, it is difficult to apply cobalt silicide directly on an ultra-shallow source/drain area. Moreover, a reduction in the junction depth requires a very flat interface between the silicide layer and the silicon active layer.
Nickel silicide is more suitable for ultra-shallow junction applications because nickel monosilicide (NiSi) consumes only 1.83 Angstoms (xc3x85) of Si per xc3x85 of nickel (Ni) as compared with 3.64 xc3x85 of Si per xc3x85 of cobalt (Co) needed to form CoSi2. Moreover, epitaxial silicide is the ideal material for shallow junctions because of the lack of any preturbation from individual grains, plus the advantages of higher thermal stability and lower resistivity and interfacial stress. However, NiSi is not stable at temperatures higher than 700xc2x0 C. In particular, the NiSi further reacts with Si to convert to NiSi2, and at higher temperatures agglomerates to isolate islands within the film. Because future advanced integrated circuit (IC) processes will involve high temperatures, it is important to establish a method to form a silicide on an ultra-shallow junction which will be stable at temperatures of about 800xc2x0 C. or higher.
Adding platinum (Pt) to improve the thermal stability of nickel silicide has been discussed. However, it has been observed that electrically active defects in N-type Si were induced by the addition of Pt. The addition of Iridium (Ir) to a nickel silicide has been shown to improve the stability of the nickel silicide up to temperatures of 850xc2x0 C. Moreover, good junction integrity in 40 nm ultra-shallow junctions was demonstrated. However, Iridium has not been used to fabricate epitaxial nickel disilicides because iridium is not easily etchable during a selective etch process.
Based on the disadvantages of these prior art silicides, there is a need for a method to form an epitaxial nickel disilicide on (100) Si. It is widely believed that epitaxial silicide will be desirable for use in future devices having very shallow junctions. Epitaxial silicide films in general have a very smooth silicide to Si interface. Due to the lack of grain boundaries, these films have high thermal stability and low resistivity.
The lattice mismatch between cobalt discilicide and Si is only xe2x88x921.4%. The lattice mismatch between nickel disilicide and Si is only xe2x88x920.4%. It is known that single crystal nickel disilicide can be formed on (111) Si by depositing Ni on Si and then annealing the films at a high temperature. The interface between the silicide and the (111) Si is very smooth, as shown in FIG. 1. However, when depositing nickel disilicide on (100) Si, it has been reported that serious faceting along the (111) plane is observed. A schematic of the interface of the silicide and the (100) Si is shown in FIG. 2.
A method to avoid the faceting problem in the epitaxial growth of NiSi2 on (100) Si has been reported. The method requires the co-deposition of Ni and Si. Selective formation of the silicide, therefore, can not be achieved. Accordingly, it is difficult to implement this technique to small device fabrication processes.
Accordingly, there is a need for a method to form single-crystal NiSi2 on (100) Si that is applicable to standard selective silicide processes for fabrication of devices having very small device features.
The present invention provides an integrated circuit device including an epitaxial nickel silicide on (100) Si, or a stable nickel silicide on amorphous Si, and a method of manufacturing the same. In particular, the method comprises depositing a cobalt (Co) interface layer between the Ni and Si layers prior to the silicidation reaction. The cobalt/nickel/silicon alloy film formed from the reaction of the cobalt interlayer with the nickel and silicon regulates the flux of the Ni atoms through the interlayer so that the Ni atoms reach the Si interface at a similar rate, i.e., without any orientation preference, so as to form a uniform layer of nickel silicide. Accordingly, a single crystal nickel silicide on (100) Si or on amorphous Si is achieved wherein the nickel silicide has improved stability and may be utilized in ultra-shallow junction devices. Accordingly, an object of the present invention is to provide a single-crystal NiSi2 on (100) Si without the formation of silicide faceting along the (111) plane into the Si substrate.
Another object of the present invention is to provide a nickel silicide fabrication process that is compatible with proposed future IC fabrication processes, allows selective formation of the silicide, and is inexpensive and simple to conduct.
Yet another object of the present invention is to provide a nickel silicide film for use in ultra-shallow junctions having a junction depth less than 40 nm, while maintaining the junction integrity and stability of the silicide layer at temperatures above 800xc2x0 C., wherein cobalt is incorporated into the silicide layer.